1. Field of the Invention
The present invention relates to a system for extending communication equipment. More particularly, the invention relates to a system for extending communication equipment using flat coaxial cables, the system dealing flexibly with making extensions and interface changes to the equipment.
2. Description of the Related Art
Today, there exist communication equipment extension systems that are used to make optical channel extensions and interface changes to optical communication equipment. Typically, the extension system is interposed between exchange and transmitter or between transmitters of an optical communication system, providing the necessary extensions without hampering overall optical circuit controls such as selection, changing, switching and testing of optical circuits.
There are three kinds of optical transmission trunk systems worldwide: one of Japan, another of North America and another of Europe. Because these systems were developed independently of one another, the digital hierarchy of optical circuit channels differ from region to region. Attempts to unify the digital hierarchies worldwide were launched in recent years, and the individual countries involved began studying ways to attain the unified specifications. In 1988, the CCITT established the Synchronous Digital Hierarchy (SDH). The move was accompanied by the adoption of recommendations for inter-communication network standardization. Thus the stage was set for building optical communication trunk networks unified worldwide.
Conventional systems for extending communication equipment primarily involve replacing printed wiring board assemblies (hereinafter called PWB assemblies) on shelves to accomplish interface changes or equipment extensions. Because it is on the level of PWB assemblies that the conventional communication equipment extension systems provide equipment extensions or interface changes, these systems are incapable of complying flexibly with the universal standard optical trunk communication network.
To set up a new optical communication network requires that the network be extended on the shelf level, that the space occupied the extension system be limited to a minimum, and that interface changes be made on the level of PWB assembly. Until now, at a typical network equipment site, the extension system is disproportionately large compared with the other small-sized communication equipment. The space occupied by the extension system is wasteful and needs to be reduced. Furthermore, the conventional extension system provides extensions and interface changes only on the PWB assembly level. The inflexibility of the system in this respect is a significant disadvantage of the prior art.